This invention relates to reaction resin mixtures which set at room temperature and to their use for impregnating insulation of electrical apparatus and for preparing molding materials.
Reaction resin mixtures of organic polyisocyanates, organic (poly)epoxides, and special catalysts with isocyanurate and oxazolidinone structures are prepared by the polyaddition of (poly)epoxides with polyisocyanates using hardening catalysts. See European Application 130,454, German Offenlegungsschrift 3,323,084, or European Application 272,563. The use of catalysts, particularly tertiary amines, has been disclosed in German Auslegeschrift 1,115,922. The industrial application of these mixtures, however, is difficult because the known accelerators or accelerator systems (which are also mentioned, for example, in German Offenlegungsschrift 2,444,458) cause the mixtures to harden either too rapidly or too slowly, thereby preventing the economical production of insulation or molding materials containing such mixtures of accelerators. These difficulties can arise when the viscosity of the reaction resin mixture sometimes rises too rapidly for complete impregnation or instantaneous reactions that lead to the formation of jellylike deposits take place at the surface of contact of the resin when the accelerators are introduced into the reaction resin mixtures. When the accelerator systems are relatively slow to react, however, hardening at room temperature does not take place within an economically acceptable period of time. A further disadvantage is the unpleasant odor of the aminic accelerators known in the art.
It is therefore an object of the present invention to develop reaction resin mixtures which harden at room temperature from polyisocyanate-(poly)epoxide resin compounds that are relatively free from odor and will not undergo an instantaneous change in viscosity at room temperature but which still harden with sufficient rapidity to be economical.